Your visual field refers to how much you can see around you, including objects in your peripheral (side) vision. This test produces a map of your field of vision. Visual field tests help your ophthalmologist monitor any loss of vision and diagnose eye problems and disease..

The test is performed

  with a large, bowl-shaped instrument called a perimeter. In order to test one eye at a time, one of your eyes is temporarily patched during the test. You will be seated and positioned comfortably in front of the perimeter and asked to look straight ahead at a fixed spot (the fixation target).

The computer randomly flashes points of light around the bowl-shaped perimeter. When you see a light, press the indicator button. It is very important to always keep looking straight ahead. Do not move your eyes to look for the target; wait until it appears in your side vision. It is normal for some of the lights to be difficult to see.

 A delay in seeing a light does not necessarily mean your field of vision is damaged. If you need to rest during the test, tell the technician and they will pause the test until you are ready to continue.

 Your ophthalmologist will interpret the results of your test and discuss them with you. If you are diagnosed with a particular disorder or disease such as glaucoma, visual field tests become a routine part of your treatment.